The present invention relates to a catalyst for production of a polyurethane resin such as a flexible polyurethane foam, a semi-rigid polyurethane foam, a rigid polyurethane foam or a polyurethane elastomer, and a method for producing a polyurethane resin employing such a catalyst. More particularly, it relates to a catalyst and a method for producing a polyurethane resin and a polyurethane foam, which do not substantially discharge a volatile amine.
A polyurethane resin is produced by reacting a polyol with a polyisocyanate in the presence of a catalyst and, if necessary, a blowing agent, a surfactant, a cross-linking agent, etc. Heretofore, it has been known to employ various metal compounds or tertiary amine compounds as catalysts for production of such polyurethane resins. These catalysts are industrially used alone or in combination.
Among these catalysts, tertiary amine compounds are particularly excellent in productivity and moldability and thus widely used as tertiary amine catalysts for production of polyurethane resins. They include, for example, conventional compounds such as triethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl)ether, N,N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-pentamethyldiethylenetriamine, N-methylmorpholine, N-ethylmorpholine and N,N-dimethylethanolamine.
Metal catalysts tend to be poor in productivity and moldability, and in most cases, they are used in combination with tertiary amine catalysts, and they are rarely employed alone.
However, the tertiary amine catalysts will remain in a free form in polyurethane resin products and will gradually be discharged as volatile amines, whereby various problems will be brought about. For example, a volatile amine discharged from a polyurethane foam in the interior of an automobile creates an odor problem. Further, in recent years, there has been a so-called fogging problem, such that a volatile component in a polyurethane foam will deposit on a window glass of an automobile thereby to bring about fogging of the window glass and thereby to reduce the commercial value. In addition to such problems, there is a pollution problem such that a volatile amine discharged from such a polyurethane product will pollute other materials.
As a method for solving such problems caused by the volatile tertiary amine catalysts, it has been proposed to employ an amine catalyst having in its molecule, primary and secondary amino groups or a hydroxyalkyl group which is capable of reacting with a polyisocyanate (JP-A-46-4846, JP-A-59-191743, JP-B-61-31727, JP-B-57-14762). It is said that the above problems can be avoided, since the amine catalyst will be fixed in the polyurethane resin skeleton in the form as reacted with a polyisocyanate.
However, most of such amine catalysts having a reactive group undergo an incomplete reaction, and a small amount thereof will remain in a free form in polyurethane resin products and will gradually be discharged as volatile amines. Further, although they may once react with the polyisocyanate and be fixed in the polyurethane resin skeleton, they will be discharged as free amines in a small amount when the polyurethane products are brought to a high temperature to bring decomposition of bonds. Further, with the amine catalysts having primary and secondary amino groups, curing of the polyurethane resin tends to be inadequate, thereby to bring about a decrease in the productivity, and further, moldability and physical properties of polyurethane products to be produced tend to be inadequate.
Further, as a method for solving such problems caused by the volatile tertiary amine catalysts, it has been proposed to employ an amine catalyst having a ureide group (such as CONH2) in its molecule (JP-A-61-85431). It is disclosed that with such an amine catalyst having a ureide group, volatility and odor tend to decrease as compared with an amine catalyst having no such functional group. Further, it is disclosed that the catalyst having a ureide group is fixed in the polyurethane resin skeleton in the form as reacted with a polyisocyanate, whereby the fogging problem may be avoided. However, the amine catalyst having a ureide group usually has a low or modest level of catalytic activity, whereby productivity of the urethane resin tends to be poor.
Further, metal catalysts other than the amine catalysts, such as organic tin compounds, will not bring about the above problems, but by their single use, the productivity, physical properties and moldability tend to be poor, and further, environmental problems due to metals remaining in products have been pointed out.
The present invention has been made in view of the above problems, and its object is to provide a method for producing such a polyurethane resin that substantially no amine is discharged from products, with good productivity and moldability, and a catalyst to be used for the method.
The present inventors have conducted extensive studies to overcome the above problems and as a result, have found that substantially no volatile amine is generated, no decomposition of bonds takes place, and further, a polyurethane resin can be obtained with good moldability and productivity, by using as an amine catalyst in production of a polyurethane resin, a catalyst selected from the group consisting of a catalyst (A) containing an amine compound of the following formula (1): 
wherein each of R1 and R2 which are independent of each other, is a C1-4 alkyl group, and A is a C5-10 straight chain or branched chain alkylene group, which contains one primary amino group and one tertiary amino group in its molecule, the carbon number of the alkylene group between the two amino groups being from 5 to 10; a catalyst (B) containing an amine compound of the following formula (2): 
which has a quinuclidine skelton containing a primary amino group in its molecule;
a catalyst (C) containing a urea-addition product of 3-aminoquinuclidine of the following formula (3): 
a catalyst (D) containing an amine compound of the following formula (5): 
wherein each of R3, R4 and R5 which are independent of one another, is a hydrogen atom or a C1-4 alkyl group, R6 is a hydrogen atom, a functional group of the following formula: 
wherein R7 is a hydrogen atom or a C1-4 alkyl group, and p is an integer of from 1 to 3, or a 3-aminopropyl group, and an amine compound of the following formula (6): 
wherein X is a nitrogen atom or an oxygen atom, each of R8 and R9 which are independent of each other, is a methyl group or a functional group of the following formula: 
wherein R10 is a hydrogen atom or a C1-4 alkyl group, and q is an integer of from 1 to 3, and each of m and n is an integer of from 1 to 2, provided that when X is a nitrogen atom, R8 and R9 are not simultaneously methyl groups, and that when X is an oxygen atom, R9 is a functional group of the following formula: 
wherein R10 is a hydrogen atom or a C1-4 alkyl group, and q is an integer of from 1 to 3; and
a catalyst (E) containing an amine compound of the following formula (7): 
wherein each of R11, R12 and R13 which are independent of one another, is a hydrogen atom or a C1-4 straight chain or branched chain alkyl group, and R14 is a C1-4 straight chain or branched chain alkylene group. The present invention has been accomplished on the basis of this discovery.
Namely, the present invention provides a method for producing a polyurethane resin, which comprises reacting a polyol with a polyisocyanate in the presence of a catalyst selected from the group consisting of the above catalysts (A), (B), (C), (D) and (E), and a catalyst for production of a polyurethane resin.
Now, the present invention will explained in detail with reference to the preferred embodiments.
In the present invention, the amine compound of the formula (1) contains one primary amino group and one tertiary amino group in its molecule, and the carbon number of the alkylene group between the two amino groups is from 5 to 10. The carbon number is preferably from 5 to 8 in view of the amount of the amine remaining in the polyurethane resin and catalytic activity, and it is particularly preferably 5 or 6.
Here, it has been proposed to employ a dialkyl-substituted primary amine such as dimethylaminopropylamine or diethylaminoethylamine as a catalyst for production of a polyurethane foam (JP-A-46-4846).
However, with this method, there are problems of odor and toxicity similar to conventional volatile tertiary amines, and there is such a problem that flowability at the time of foaming tends to be poor, whereby every hole and corner of a mold may not be filled with the reaction product(JP-A-59-191743).
Accordingly, JP-A-59-191743 discloses to employ a carbonate of the dialkyl-substituted primary amine to overcome the problems of the method of JP-A-46-4846.
For example, it discloses that there is no odor at the time of removal from a mold, since all the catalyst molecules having primary amino groups (xe2x80x94NH2) in their molecules, react with isocyanate groups and chemically bonded to the polymer skeleton. Further, it disclose that the alkylene group in the dialkyl-substituted primary amine is preferably an ethylene, n-propylene or n-butylene group in view of catalytic activity.
However, according to studies by the present inventors, it was found that a carbonate of a dialkyl-substituted primary amine having an ethylene, n-propylene or n-butylene group as the alkylene group which is disclosed as a preferred catalyst in JP-A-59-191743, has a low catalytic activity, whereby the productivity tends to be low in production of a polyurethane resin, and further, the moldability tends to be poor. It is also found that the dialkyl-substituted primary amine tends to remain in a large amount in a free form in the urethane resin along with the increase in the carbon number of the alkylene group, whereby the odor tends to be significant.
On the other hand, the present inventors have found that the amine compound of the formula (1) of the present invention has a specifically high catalytic activity and significantly improves productivity and moldability, and in addition, it remains only in a small amount in a free form in the urethane resin, whereby a foam which gives a reduced amine odor can be obtained. Accordingly, the present invention has especial effects which are unexpectable from prior arts.
The amine compound of the present invention may, for example, be N,N-dimethylpentamethylenediamine, N,N-dimethylhexamethylenediamine, N,N-dimethylheptamethylenediamine, N,N-dimethyloctamethylenediamine, N,N-dimethylnonamethylenediamine, N,N-dimethyldecamethylenediamine, N,N-diethylpentamethylenediamine, N,N-diethylhexamethylenediamine, N,N-diethylheptamethylenediamine, N,N-diethyloctamethylenediamine, N,N-diethylnonamethylenediamine, N,N-diethyldecamethylenediamine, N,N-dipropylpentamethylenediamine, N,N-dipropylhexamethylenediamine, N,N-dipropylheptamethylenediamine, N,N-dipropyloctamethylenediamine, N,N-dipropylnonamethylenediamine, N,N-dipropyldecamethylenediamine, N,N-dibutylpentamethylenediamine, N,N-dibutylhexamethylenediamine, N,N-dibutylheptamethylenediamine, N,N-dibutyloctamethylenediamine, N,N-dibutylnonamethylenediamine or N,N-dibutyldecamethylenediamine. Among them, more preferred are N,N-dimethylpentamethylenediamine and N,N-dimethylhexamethylenediamine having a high catalytic activity.
The amine compound of the formula (1) contained in the catalyst (A) of the present invention can easily be produced by a known method. A method may, for example, be mentioned, wherein a dialkyl amine is reacted with bromoalkyl-N-phthalimide obtained by a reducing amination reaction of a dialkylaminoalkanol with ammonia or by a reaction of an alkyl dibromide with potassium phthalimide in the presence of excess alkyl dibromide, and then hydrazine is reacted therewith.
The amount of the catalyst (A) of the present invention in production of a polyurethane resin is from 0.01 to 10 parts by weight, preferably from 0.05 to 5 parts by weight, per 100 parts by weight of the polyol to be used. If a large amount of the catalyst is used, the productivity of the polyurethane resin may improve, but the amount of a volatile amine also increase, such being unfavorable.
The catalyst (B) for production of a polyurethane resin of the present invention contains 3-aminoquinuclidine of the formula (2).
The amine compound of the formula (2) contained in the catalyst (B) of the present invention can easily be produced, for example, by neutralizing commercially available 3-aminoquinuclidine dihydrochloride with an alkali metal aqueous solution. Specifically, a method wherein 3-aminoquinuclidine dihydrochloride (manufactured by Aldlich) is neutralized with a 48% sodium hydroxide aqueous solution, followed by extraction with benzene, may, for example, be mentioned.
The amount of the catalyst (B) of the present invention in production of a polyurethane resin is from 0.01 to 10 parts by weight, preferably from 0.05 to 5 parts by weight, per 100 parts by weight of the polyol to be used. If a large amount of the catalyst is used, the productivity of the polyurethane resin may improve, but the amount of a volatile amine also increase, such being unfavorable.
The catalyst (C) for production of a polyurethane resin of the present invention contains an amine compound of the formula (3). Further, the catalyst (C) for production of a polyurethane resin of the present invention may contain the amine compound of the formula (3) and an amine compound of the following formula (4): 
The catalyst (C) of the present invention preferably contains from 50 to 95 wt % of the amine compound of the formula (3) and from 5 to 50 wt % of the compound of the formula (4), based on the total amount of the compound of the formula (3) and the compound of the formula (4). If the amine compound of the formula (3) is less than 50 wt %, the catalytic activity tends to be low, whereby productivity of the polyurethane resin tends to be poor.
The amine compound of the formula (3) and the amine compound of the formula (4) may be produced, for example, by reacting urea and 3-aminoquinuclidine in an appropriate molar ratio under heating. Accordingly, the catalyst (C) of the present invention may contain unreacted urea in an amount up to 20 wt %. The compound of the formula (3) and the compound of the formula (4) may separately be isolated by e.g. chromatography, recrystallization, sublimation or distillation.
The amount of the catalyst (C) of the present invention in production of a polyurethane resin is from 0.01 to 10 parts by weight per 100 parts by weight of the polyol to be used. It is preferably from 0.05 to 5 parts by weight, since if a large amount of the catalyst is used, the amount of the catalyst to be incorporated in the polyurethane resin as a terminator tends to be large, whereby physical properties (functional properties) of the resin tend to be deteriorated.
The catalyst (D) for production of a polyurethane resin of the present invention contains an amine compound of the formula (5) and an amine compound of the formula (6).
In the present invention, the compound of the formula (5) is an imidazole compound having a reactive group. In view of catalytic activity, preferably R3 is a hydrogen atom or a methyl group, each of R4 and R5 is a hydrogen atom, and R6 is a 2-hydroxypropyl group, a 2-hydroxyethyl group or a 3-aminopropyl group.
Specifically, the amine compound of the formula (5) of the present invention may, for example, be imidazole, 2-methylimidazole, 1-(2xe2x80x2-hydroxypropyl)-imidazole, 1-(2xe2x80x2-hydroxypropyl)-2-methylimidazole, 1-(2xe2x80x2-hydroxyethyl)-imidazole, 1-(2xe2x80x2-hydroxyethyl)-2-methylimidazole, 1-(3xe2x80x2-aminopropyl)-imidazole, 1-(3xe2x80x2-aminopropyl)-2-methylimidazole, 1-(3xe2x80x2-hydroxypropyl)-imidazole or 1-(3xe2x80x2-hydroxypropyl)-2-methylimidazole. Among them, preferred are 1-(2xe2x80x2-hydroxypropyl)-imidazole, 1-(2xe2x80x2-hydroxypropyl)-2-methylimidazole, 1-(2xe2x80x2-hydroxyethyl)-imidazole, 1-(2xe2x80x2-hydroxyethyl)-2-methylimidazole, 1-(3xe2x80x2-aminopropyl)-imidazole and 1-(3xe2x80x2-aminopropyl)-2-methylimidazole in view of high catalytic activity.
The amine compound of the formula (6) of the present invention is a tertiary amine catalyst having a reactive group, and it may, for example, be N-(2-hydroxypropyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxypropyl)-N,N,Nxe2x80x3,Nxe2x80x3N-tetramethyldiethylenetriamine, N-(2-hydroxyethyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxyethyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, N-(2-hydroxybutyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxybutyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, N-(2-hydroxypentyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxypentyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, N-(2-hydroxyhexyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxyhexyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxypropryl)-N,N,Nxe2x80x2-trimethyl-bis(2-aminoethyl)ether, Nxe2x80x2-(2-hydroxyethyl)-N,N,Nxe2x80x2-trimethyl-bis(2-aminoethyl)ether and Nxe2x80x2-(2-ethoxyethanol)-N,N,Nxe2x80x2-trimethyl-bis(2-aminoethyl)ether. Among them, preferred are N-(2-hydroxyethyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxyethyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, N-(2-hydroxypropyl)-N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxypropyl)-N,N,Nxe2x80x3,Nxe2x80x3-tetramethyldiethylenetriamine, Nxe2x80x2-(2-hydroxypropryl)-N,N,Nxe2x80x2-trimethyl-bis(2-aminoethyl)ether and Nxe2x80x2-(2-hydroxyethyl)-N,N,Nxe2x80x2-trimethyl-bis(2-aminoethyl)ether in view of high catalytic activity.
The amine compound of the formula (5) and the amine compound of the formula (6) contained in the catalyst (D) of the present invention can easily be produced by a known method respectively. The compound of the formula (5) is obtained, for example, by reacting 2-methylimidazole with acrylonitrile, followed by amination by hydrogenation or by a reaction of 2-methylimidazole with propylene oxide or ethylene oxide. Further, the compound of the formula (6) may be obtained, for example, by reacting diethylene triamine with propylene oxide, followed by reducing methylation.
If the compound of the formula (5) or the compound of the formula (6) in the catalyst (D) of the present invention is used for production of a polyurethane resin by itself, the productivity and moldability of the products tend to be poor, and further, the amount of the amine to be discharged from the products can not adequately be decreased. Namely, the compound of the formula (5) has a low catalytic activity, and a large amount thereof is required, whereby it is likely to remain as an amine in a free form in a polyurethane resin, and the amount of an amine to be discharged tends to increase. Further, curing of the polyurethane resin tends to be slow, whereby productivity tends to be poor. The compound of the formula (6) has a high catalytic activity, and thus curing of the polyurethane resin tends to be quickened, however, there is a problem in moldability such that foam products may shrink or deform.
However, surprisingly, when the compound of the formula (5) and the compound of the formula (6) are mixed, the catalytic activity as a catalyst mixture becomes high by a synergistic effect, and the amount of the catalyst can be decreased, and as a result, the amount of an amine to be discharged is small. Further, curing of the polyurethane resin tends to be quickened, stability of the foam can be increased, and products having a good moldability without deformation can be obtained.
The mixing ratio in the catalyst composition of the present invention is not particularly limited, but the proportion of the compound of the formula (5) to the compound of the formula (6) is preferably from 1/9 to 9/1 by a weight ratio. It is more preferably from 3/7 to 7/3.
The amount of the catalyst (D) of the present invention in production of a polyurethane resin is from 0.01 to 10 parts by weight per 100 parts by weight of the polyol to be used, and it is preferably from 0.01 to 7 parts by weight in order to further reduce the amine to be discharged.
The catalyst (E) of the present invention contains a compound of the formula (7). The catalyst of the present invention may further contain, in addition to the compound of the formula (7), a compound of the following formula (8): 
wherein each of R15, R16 and R17 which are independent of one another, is a hydrogen atom or a C1-4 straight chain or branched chain alkyl group, and R18 is a C1-4 straight chain or branched chain alkylene group.
The catalyst (E) of the present invention preferably contains from 50 to 100 wt % of the compound of the formula (7) and from 0 to 50 wt % of the compound of the formula (8) based on the total amount of the compound of the formula (7) and the compound of the formula (8). If the compound of the formula (7) is less than 50 wt %, the catalytic activity tends to be low, and productivity of the polyurethane resin may decrease.
In the present invention, the compound of the formula (7) is preferably a compound wherein R11 is a hydrogen atom or a methyl group, each of R12 and R13 is a hydrogen atom, and R14 is a propylene group, in view of catalytic activity and easiness in production. Further, the compound of the formula (8) is preferably a compound wherein R15 is a hydrogen atom or a methyl group, each of R15 and R17 is a halogen atom, and R18 is a propylene group, in view of catalytic activity and easiness in production.
Specifically, the amine compound of the formula (7) of the present invention may, for example, be 1-{3xe2x80x2-(imidazolinyl)propyl}urea, 1-{3xe2x80x2-(2xe2x80x3-methylimidazolinyl)propyl}urea, 1-{2xe2x80x2-(imidazolinyl)ethyl}urea, 1-{2xe2x80x2-(2xe2x80x3-methylimidazolinyl)ethyl}urea, 1-{2xe2x80x2-(imidazolinyl)-1xe2x80x2-methylethyl}urea or 1-{2xe2x80x2-(2xe2x80x3-methylimidazolinyl)-1xe2x80x2-methylethyl}urea. Among them, more preferred are 1-{3xe2x80x2-(imidazolinyl)propyl}urea and 1-{3xe2x80x2-(2xe2x80x3-methylimidazolinyl)propyl}urea in view of easiness in synthesis.
Specifically, the amine compound of the formula (8) of the present invention may, for example, be 1,3-bis{3xe2x80x2-(imidazolinyl)propyl}urea, 1,3-bis{3xe2x80x2-(2xe2x80x3-methylimidazolinyl)propyl}urea, 1,3-bis{2xe2x80x2-(imidazolinyl)ethyl}urea, 1,3-bis{2xe2x80x2-(2xe2x80x3-methylimidazolinyl)ethyl}urea, 1,3-bis{2xe2x80x2-(imidazolinyl)-1xe2x80x2-methylethyl}urea or 1,3-bis{2xe2x80x2-(2xe2x80x3-methylimidazolinyl)-1xe2x80x2-methylethyl}urea. Among them, more preferred are 1,3-bis{3xe2x80x2-(imidazolinyl)propyl}urea and 1,3-bis{3xe2x80x2-(2xe2x80x3-methylimidazolinyl)propyl}urea in view of easiness in synthesis.
The compounds of the formulae (7) and (8) can be produced, for example, by reacting urea with a 1-(3xe2x80x2-aminopropyl)imidazole in an appropriate molar ratio under heating. Accordingly, the catalyst (E) of the present invention may contain unreacted urea in an amount of up to 20 wt %. The compounds of the formulae (7) and (8) can separately be isolated by means of e.g. chromatography, recrystallization or sublimation.
The amount of the catalyst (E) of the present invention in production of a polyurethane resin is usually from 0.01 to 10 parts by weight per 100 parts by weight of the polyol to be used. It is preferably from 0.05 to 5 parts by weight since if the amount of the catalyst is large, the amount of the catalyst to be incorporated in the polyurethane resin as a terminator tends to be large, whereby physical properties (functional properties) of the resin may decrease.
The catalyst (A), (B) and (D) of the present invention will react with a polyisocyanate which is a material for a polyurethane resin, and fixed in the polyurethane resin skeleton. Further, the fixed catalysts of the present invention will not be decomposed even when exposed to a high temperature. Thus, the catalysts of the present invention will not be present in the form of a free amine in the polyurethane resin, and accordingly, no volatile amine will be discharged.
Further, the catalysts (C) and (E) of the present invention have extremely low volatility and odor. Further, they will react with a polyisocyanate which is a material for a polyurethane resin, and fixed in the polyurethane resin skeleton.
Namely, in a case where the catalysts of the present invention is used, the working environment in production of a polyurethane is improved, and further, it becomes possible to prevent the above-described various problems, such as an odor due to a volatile amine and fogging.
The method for producing a polyurethane resin employing the catalyst of the present invention is a method for obtaining a polyurethane resin product by reacting a polyol with a polyisocyanate in the presence of the catalyst and, if necessary, e.g. a blowing agent, a surfactant or a cross-linking agent. The polyurethane product may, for example, be a flexible polyurethane foam, a semi-rigid polyurethane foam or a rigid polyurethane foam, to be produced by means of a blowing agent, or a polyurethane elastomer product to be produced without using a blowing agent. Among such products, the catalysts of the present invention are applicable preferably to a flexible polyurethane foam, a semi-rigid polyurethane foam or a rigid polyurethane foam, to be produced by means of a blowing agent.
In the polyurethane resin produced by using the catalyst (A) of the present invention, the amount of the volatile amine catalyst is at most 300 xcexcg per g of the polyurethane resin, and it is more preferably at most 100 xcexcg/g in view of environment in an automobile.
Further, in the polyurethane resin produced by using the catalyst (B) of the present invention, the amount of the volatile amine catalyst is at most 20 xcexcg per g of the polyurethane resin.
Here, in the present invention, the amount of the volatile amine catalyst is the total amount of the amine catalyst generated from a polyurethane resin when the polyurethane resin is heated in a methanol solvent at 65xc2x0 C. for 48 hours.
The polyol to be used in the method for producing a polyurethane resin of the present invention, includes, for example, conventional polyether polyols, polyester polyols, polymer polyols and further flame resisting polyols such as phosphorus-containing polyols or halogen-containing polyols. These polyols may be used alone or in a proper combination as mixed.
The polyether polyols can be produced, for example, by an addition reaction of an alkylene oxide such as ethylene oxide or propylene oxide to a starting material which is a compound having at least two active hydrogen groups, such as a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerol, trimethylol propane or pentaerythritol, an amine such as ethylenediamine, or an alkanolamine such as ethanolamine or diethanolamine, for example, by a method disclosed in xe2x80x9cPolyurethane Handbookxe2x80x9d edited by Gunter Oertel (1985), Hanser Publishers (Germany), p.42-53.
The polyester polyols may, for example, be those obtainable by a reaction of a dibasic acid with glycol, further a waste during production of nylon as disclosed in xe2x80x9cPolyurethane Resin Handbookxe2x80x9d edited by Keiji Iwata, (first edition published in 1987), THE NIKKAN KOGYO SHIMBUN, LTD., p.117, trimethylolpropane, a waste of pentaerythritol, a waste of a phthalate type polyester, and polyester polyols derived from treatments of such waste products.
The polymer polyols may, for example, be polymer polyols obtained by reacting the above-mentioned polyether polyol with an ethylenically unsaturated monomer such as butadiene, acrylonitrile or styrene, in the presence of a radical polymerization catalyst.
The flame resisting polyols may, for example, be phosphorus-containing polyols obtainable by adding an alkylene oxide to a phosphoric acid compound, halogen-containing polyols obtainable by ring opening polymerization of epichlorohydrin or trichlorobutylene oxide, and phenol polyols.
These polyols may have molecular weights of from 62 to 15,000.
For flexible polyurethane foams, those having molecular weights of from 1,000 to 15,000 may be used. Preferred are polyether polyols and polymer polyols having molecular weights of from 3,000 to 15,000. If the molecular weight is smaller than 3,000, e.g. physical properties (elasticity) tend to be poor in some cases, and accordingly preferred are ones having molecular weights of at least 3,000. More preferred are flexible polyurethane foams prepared by using polyether polyols and polymer polyols in combination. The polymer polyols have an effect to increase the strength (hardness, elastic properties) of a resin, whereby the molecular design (hardness, elastic properties) becomes easy.
For rigid polyurethane foams, those having molecular weights of from 62 to 8,000 may be used. Preferred are polyether polyols having molecular weights (Mw) of from 62 to 1,500. The polyols for rigid polyurethane foams are preferably those having a large number (4-8) of functional groups and having low molecular weights.
The polyisocyanate to be used in the present invention may be a known polyisocyanate and is not particularly limited, and it may, for example, be an aromatic polyisocyanate such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthylene diisocyanate or xylylene diisocyanate, an aliphatic polyisocyanate such as hexamethylene diisocyanate, an alicyclic polyisocyanate such as dicyclohexyl diisocyanate or isophorone diisocyanate, or a mixture thereof. As TDI or its derivative, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, or a terminal isocyanate prepolymer derivative of TDI, may be mentioned. As MDI or its derivative, a mixture of MDI and its polymer i.e. a polyphenyl-polymethylene diisocyanate, and/or a terminal isocyanate group-containing diphenylmethane diisocyanate derivative, may be mentioned. Among such organic polyisocyanates, TDI and MDI are preferably employed.
The ratio of such a polyisocyanate to the polyol is not particularly limited, but, as represented by an isocyanate index (i.e. isocyanate groups/active hydrogen groups reactive with isocyanate groups), it is usually within a range of from 60 to 130 for the production of a flexible polyurethane foam or a semi-rigid polyurethane foam and usually within a range of from 60 to 400 for the production of a rigid polyurethane foam or a polyurethane elastomer.
The catalyst to be used for the method for producing a polyurethane resin of the present invention, is the above-mentioned catalyst of the present invention. However, other catalysts may be used in combination within a range not to depart from the present invention. As such other catalysts, for example, conventional organic metal catalysts, tertiary amines or quaternary ammonium salts may be mentioned.
The organic metal catalysts include, for example, stannous diacetate, stannous dioctoate, stannous dioleate, stannous dilaurate, dibutyltin oxide, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, dioctyltin dilaurate, lead octanoate, lead naphthenate, nickel naphthenate and cobalt naphthenate.
The tertiary amines may be conventional ones, for example, tertiary amine compounds such as N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2,-tetramethylpropylenediamine, N,N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-pentamethyldiethylenetriamine, N,N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-pentamethyl-(3-aminopropyl)ethylenediamine, N,N,Nxe2x80x2,Nxe2x80x3,Nxe2x80x3-pentamethyldipropylenetriamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylguanidine, 1,3,5-tris(N,N-dimethylaminopropyl)hexahydro-S-triazine, 1,8-diazabicyclo[5.4.0]undecene-7, triethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexamethylenediamine, N-methyl-Nxe2x80x2-(2-dimethylaminoethyl)piperazine, N,Nxe2x80x2-dimethylpiperazine, dimethylcyclohexylamine, N-methylmorpholine, N-ethylmorpholine, bis(2-dimethylaminoethyl)ether, 1-methylimidazole, 1,2-dimethylimidazole, 1-isobutyl-2-methylimidazole and 1-dimethylaminopropylimidazole. Further, tertiary amine compounds having reactive groups other than the present invention may also be used, such as dimethylethanolamine, dimethylisopropanolamine, N,N-dimethylhexanolamine, dimethylaminoethoxyethanol, N,N-dimethyl-Nxe2x80x2-(2-hydroxyethyl)ethylenediamine, N,N-dimethyl-Nxe2x80x2-(2-hydroxyethyl)propanediamine, N-methyl-Nxe2x80x2-(2-hydroxyethyl)piperazine, bis(dimethylaminopropyl)amine, bis(dimethylaminopropyl)isopropanolamine, 1-(2-hydroxyethyl)imidazole, 1-(2-hydroxypropyl)imidazole, 1-(2-hydroxyethyl)-2-methylimidazole, 1-(2-hydroxypropyl)-2-methylimidazole and 3-quinuclidinol.
The quaternary ammonium salts include, for example, conventional tetraalkylammonium halides such as a tetramethylammonium chloride, tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, and tetraalkylammonium organic acid salts such as a tetramethylammonium 2-ethylhexanoate, a 2-hydroxypropyltrimethylammonium formate and a 2-hydroxypropyltrimethylammonium 2-ethylhexanoate.
The blowing agent to be used for the method for producing a polyurethane resin of the present invention, is water and/or a low boiling point organic compound. The low boiling point organic compound may, for example, be a hydrocarbon compound or a halogenated hydrocarbon compound. The hydrocarbon compound may, for example, be known methane, ethane, propane, butane, pentane or hexane. The halogenated hydrocarbon may, for example, be known halogenated methane, halogenated ethane or fluorinated hydrocarbon, such as methylene chloride, HCFC-141b, HFC-245fa or HFC-356mfc. When such blowing agents are to be used, water and a low boiling point organic compound may be used alone independently or in combination. A particularly preferred blowing agent is water. The amount may vary depending upon the density of the product, but it is usually at least 0.1 part by weight, preferably from 0.5 to 10 parts by weight, per 100 parts by weight of the polyol.
In the present invention, a surfactant may also be employed, as the case requires. As the surfactant to be used in the present invention, a conventional organic silicone type surfactant may be mentioned, and it is used usually in an amount of from 0.1 to 10 parts by weight, per 100 parts by weight of the polyol.
In the present invention, a cross-linking agent or a chain extender may be incorporated, as the case requires. As the cross-liking agent or the chain extender, a polyhydric alcohol having a low molecular weight such as ethylene glycol, 1,4-butanediol or glycerol, an aminepolyol having a low molecular weight such as diethanolamine or triethanolamine or a polyamine such as ethylenediamine, xylylenediamine or methylenebis-orthochloroaniline may, for example, be mentioned. Among them, dimethanolamine or triethanolamine is preferred.
In the method of the present invention, a coloring agent, a flame retardant, an aging-preventive agent or other known additives may also be used, as the case requires. The types and the amounts of such additives may usually be within the commonly employed ranges so long as they will not depart from known manners and procedures.
The product produced by the method of the present invention can be used for various applications, but it is particularly suitable for foam products to be produced by means of a blowing agent. A flexible polyurethane foam may, for example, be applied as a cushion to a bed, a car seat or a mattress. A semi-rigid polyurethane foam may be applied, for example, to an instrumental panel, a headrest or a steering wheel relating to an automobile. A rigid polyurethane foam may be applied, for example, to a refrigerator, a freezer or a heat-insulating building material.
A polyurethane elastomer product may, for example, be applied to an adhesive, a floor material or a waterproofing material.
Now, the present invention will be described in further detail with reference to Examples and Comparative Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples.